CBF21202 i just got an action replay from walmart and the same shit happens to me, it says that "The disc could not be read. Please read the NINTENDO GAMECUBE Instruction Booklet for more information." i dont know if yours says that but that what mines says.
i got the memory card in the B slot and i tried holding the button on my wavebird, even switched the controller to a regular corded one and still got the message. even tried switching the slot of the AR card, still got the same message.
i have a metriod bundle gamecube if that helps. i notice on the action replay box says it is made in england.